Endogenous Kv2.1 preferentially accumulates in a MAP2-negative neurite. Hippocampal cultures grown for 7, 10, 14 and 21 days were fixed and immunostained for endogenous Kv2.1 (green) and the dendritic marker MAP2 (red). At 7 DIV, the strongest labeling for Kv2.1 in these cultures appeared in the proximal portion of a MAP2-negative process (arrow) although many neurons exhibited faint clusters evenly dispersed over the cell body and proximal neurites (arrowhead). Shown in the right hand panels are maximum projection images corresponding to Kv2.1 staining from the boxed regions. In the majority of neurons, the neurite with intense Kv2.1 labeling corresponded to the process with the least intense MAP2 staining, indicating the preferential accumulation of Kv2.1 at the proximal axon.